Adjustable piston for syringes



. l 550 2 s. Nfl-:EIN 53 ADJUSTABLE PIsToN FR sfINGEs Filed Nov. 17,1924 Aug. 18,1925.

Patented Aug. 18, 1925.

UNITED [smi-ss GEORG N. HEIN, OF SAN FRANCISCO, CALIFORNIA.

nnJusrABLn rrsroi'v non sYRIlvens.

Application flied November 17, 1924. serial no. 750,357.

To all whom t may concern:

Be it known that I, Gnonen N. HEIN, a citizen of the United States,residing at the city and county of San Francisco and State ofCalifornia, have invented certain new and useful Improvements inAdjustable Pistons for Syringes, of which the following is aspecification.

r1`he present invention relates to a syringe piston particularlydesigned to overcome the necessity of a ground fit between the piston'surface and the syringe barrel of hypoder- .mic syringes, which is nowcustomary.

The invention furthe-r" relates to the provision of a piston forhypodermic syringes which is capable of adjustment within the barrel tovary the friction against the barrel wall by simply turning or operatingthe piston head supporting rod, and further relates to a pistonconstruction designed for adjustment to shape a piston packing toprovide a pair of feathered edges projecting up- ;wardly in contact withthelbarrel wall; The present piston is designed and adjusted to fit thebarrel of a syringe to enpand and contract in its travel through thebarrel and automatically adapts itselfto varying diameters andirregularity of form in the shape of a barrel.

The invention consists primarily in a piston head formed vof a pair ofrelatively telescopic members affording a mounting for a piston packingand adapted on their adjusting movement relatively to eac i other to,position the packing carried thereby, so that either one or a pluralityof portions thereof entend upwardly to provide a feather edge or lip forengaging the barrel wall.

"With the above mentioned and other objectsvin View, the inventionconsists in the novel construction and combination of parts hereinafterdescribed, illustrated in the accompanying drawings and pointed out inthe claims hereto appended; it being understood that various changes inthe form, proi portion, size and minor details of construction withinthe scope of the claims may be resorted to without departing from thespirit or sacrificing any of thel advantages of the invention.

In the drawings illustrating the preferred embodiment of my invention-Figure 1 is a longitudinal central sectional view through a syringecontaining one embodiment of my invention.

Figure 2 is a longitudinal sectional view of the piston head with thefollower in a position reversed to that illustrated in Figure-'1.

1n the drawings, wherein like vcharacters of reference designatecorresponding parts, 1 indicates a syringe barrel of any suitable type,preferably of glass, the same being provided at one epd with a needlemounting tip 2 and open at its opposite end, as.` at 3, the type ofbarrel illustrated being of relatively large diameter adapted forcontaining 50 cc. of `liuid.

lldounted to reciprocate within the barrel 1 is a rod eiguided at theopen end of the barrel 1 by a tubular guide 5 which incunts thepivotally supported barrel bead gripping fingers 6, each 'of whichmounts a spring linger 7 contacting with the wall of the member 5. Thefingers 6 are adapted for gripping' the bead 8 atthe upper open end 3 ofthe barrel 1, and the'springs associated therewith maintain th-e fingersin raised position and prevent the same from dropping to a positiontobereceived within th-e open end of the barrel 1. The upper end of thetubular guide 5 is providedavith a threaded boss 8 on which is mounted aclamp nut 9 having a flaring skirt 10 which, on the downward threadingof the nuty on the ,guide 5, is. adapted to engage the walls ofthellingers 6 and press the same inwardly against the action of the springTto maintain the same in tight engagement'l with the bead 8. rlfhe outerend of the pieten rod fis provid d with an operating handle and theinner end thereof is reduced as at 11 and threaded as at 12.

Loosely-positioned onl the reduced end l1 of the rod 4f is a followerconsisting of a disk 13 formed on its periphery with a wall 1li disposedat rightV angles to the plane of the disk. The wall projects beyond theopposie faces of the disk 13 and its ends are bevelled in parallelplanes as at 16.

Threaded onto the threaded end 12 of the rod 4l is a piston headconsisting of a disk 17 formed with a threaded boss 18 extendingcentrally from one face thereof, and said head is provided near itsperiphery with an annular skirt 19 for reception within the confines ofthe wall 111- of the follower, 13. l

The skirt 19 affords an annular seat for an elastic packing ring 20positioned on the piston head to lie between one of the bevelled faces16 of the follower 13 and the annular inwardly bevelled face 21 formedon the piston head 17 and facing one of the portions 16.

The diameter of the follower 13 and of the piston head is less than thatof the interior of the barrel.

It will be observed that the positioned elastic washer 20 is adapted atits forward edge, overlying the bevelled wall 21, to contact with theinner surface of the barrel. rlhis frictional contact is at all timessuflicient to precludel rotation of the piston head and packing withinthe barrel and to permit actual rotation of the rod t within thethreaded boss 18.

Then it is desired to vary the frictional contact of the washer with thebarrel surface, it is only necessary* to impart axial rotation to therod 4l.

It will be observed that when the fol lower 13 and piston head arearranged as in the drawing, the opposite peripheral edges of the elasticpacking 2O are caused to ride upwardly on the bevels 1G and 21 toprovide two relatively thin feather edges contacting with the inside ofthe barrel wall. On the reversal of the follower from the positionillustrated in Fig. 1, it will be observed that the inner edge of theelastic packing 2O will be precluded from moving outwardly and that theopposite edge will be forced outwardly on the bevel 21 and provided witha single annular surface or feather edge in contact with the barrelwall.

The reversibility of the follower affords means of providing a single ordouble contact seal between the packing and the barrel wall and theadjustability of the pressure of the packing against the barrel wallenables a quick variation of pressure necessary to operate the piston.

While the invention contemplates the employment of an elastic packingring to be acted on by the piston head and follower, it is to beunderstood that in constructions where a ground surface is afforded bythe inner wall of the barrel, a nonelastic or a metallic packing may besubstituted for the elastic ring illustrated by the numeral 20.

I claim 1. A piston including a rod, a packing mounting structurecarried thereby and consisting of a head threaded thereto and arotatable follower held from longitudinal' movement thereon, said headand follower having laterally extended walls adapted for relativetelescopic movement and provided with bevelled edges, and an elasticring packing mounted on one of said walls between said bevelled edgeswhereby on the relative adjustment of said head and follower one edge ofsaid packing will be curled outwardly.

2. A piston including a rod, a packing mounting structure carriedthereby and consisting of a head threaded thereto and a rotatablefollower held from longitudinal movement thereon, said head and followerhaving parallel annular walls disposed par allel with the rod andadapted for relative telescopic movement, said follower adapted forreversed positioning on said stem and the ends of its walls beingbevelled in substantial parallel planes, said head provided with a bevelextending rearwardly from its outer peripheral surface, and an elasticpacking ring mounted on said head between said bevelled surfaces.

3. In combination with a barrel, a piston reciprocably mounted thereinand including a rod, a packing mounting structure carried thereby andconsisting of two cooperating parts, one threaded for longitudinalmovement thereon and both parts provided with annular bevelled surfaces,an elastic packing positioned around and gripping the part threaded tothe stem with its surface in contact with the barrel, whereby on axialrotation being imparted to the rod relative telescopic movement will beimparted to said parts with the bevelled surfaces acting on oppositeedges of the packing.

t. A piston including a rod, a head carried thereby and consisting of apair of cooperating members one movable longitudinally of the rod to andfrom the other, an annular elastic packing, said members formed withopposing inclined circumferential faces and affording between the same asupport for the packing, said faces adapted on the relative movement ofsaid members to flex one edge of the packing to cause the same to curloutwardly beyond the periphery of the head and provide a thin annularflexible packing edge.

In testimony whereof I have signed my name to this specification.

GEORGE N. HEIN

